An ab initio approach to many-body energies and Be2+V- dipoles in LiH crystal and clusters

A finite LiH crystal whose Coulomb potential in the central region closely approximates the Madelung potential in the unit cell of the host crystal is constructed. The beryllium ion is then introduced to initiate the Be2+V- d ipole and to examine the perfect and defect properties of LiH clusters both within the crystal and as isolated species. These include the convergence properties of many-body energies, the defect formation mechanism and hydrid e ion migration. Crystal field and overlap effects are examined. Lattice re laxation around defect sites is allowed and the optimal relaxation mode is assigned. Dipole aggregates, the cluster-lattice interaction, defect format ion energies, the free rotation of the Be2+V- dipole in two perpendicular p lanes, the energy of rotation of the cation vacancy around Be2+ and the ten dency of Be2+ to associate with the cation vacancy are examined and explain ed in relation to their scientific and technological importance.